You're trying to shrink the Recovery partition. In contrast, the article tells you to shrink the OS partition and create a bigger Recovery partition.
More information:
The update failed with a fatal error when unmounting the WIM. This is due to a lack of free space in the WinRE partition. Resizing the Recovery partition is a sure way to fix this.
Resizing the Recovery partition to 750 MB resolves the issue. That applies if you use the Windows-default winre.wim.
KB5028997: Instructions to manually resize your partition to install the WinRE update - Microsoft Support: https://support.microsoft.com/en-us/topic/kb5028997-instructions-to-manually-resize-your-partition-to-install-the-winre-update-400faa27-9343-461c-ada9-24c8229763bf
For OEM-supplied winre.wim (which has additional drivers and packages), ensure the Recovery partition's size is atleast 100 MB more than the size of the custom wim.
However, if you're hesitant, you may wait and see if Microsoft releases a fix.